Embodiments of the present disclosure generally relate to determining capture thresholds, and more particularly to methods and systems to automatically adjust test ranges based on prior measured capture thresholds.
Implantable stimulation devices or cardiac pacemakers are a class of cardiac rhythm management devices that provide electrical stimulation in the form of pacing pulses to selected chambers of the heart. As the term is used herein, a pacemaker is any cardiac rhythm management device with a pacing functionality regardless of any additional functions it may perform, such as cardioversion/defibrillation.
A pacemaker is comprised of two major components, a pulse generator and a lead. The pulse generator generates the pacing stimulation pulses and includes the electronic circuitry and the power cell or battery. The lead, or leads, is implanted within the heart and has electrodes which electrically couples the pacemaker to the desired heart chamber(s). A lead may provide both unipolar and bipolar pacing and/or sensing configurations. In the unipolar configuration, the pacing pulses are generally applied (or responses are sensed) between an electrode carded by the lead and a case of the pulse generator or an electrode of another lead within the heart. In the bipolar configuration, the pacing pulses are applied (or responses are sensed) between a pair of electrodes carried by the same lead. Recently, pacing systems have been introduced that stimulate multiple sites in the same chamber, termed multisite stimulation systems or multi-purpose pacing systems.
When the patient's own intrinsic rhythm fads, pacemakers can deliver pacing pulses to a heart chamber to induce a depolarization of that chamber, which is followed by a mechanical contraction of that chamber. Pacemakers further include sensing circuits that sense cardiac activity for the detection of intrinsic cardiac events such as intrinsic atrial depolarizations (detectable as P waves) and intrinsic ventricular depolarizations (detectable as R waves). By monitoring cardiac activity, the pacemaker circuits are able to determine the intrinsic rhythm of the heart and provide stimulation pacing pulses that force atrial and/or ventricular depolarizations at appropriate times in the cardiac cycle when required to help stabilize the electrical rhythm of the heart. This therapy is referred to as cardiac resynchronization therapy (CRT).
Recently, multi-point pacing (MPP) technology has enabled pacing at left ventricular (LV) sites to improve synchrony in cardiac resynchronization therapy (CRT) patients. Improvements in synchrony and improved hemodynamic response have been shown to depend on the MPP configuration. In the past, MPP configurations have been selected based on reducing pacing capture thresholds, avoiding atrial and phrenic nerve capture, and maximizing anatomical distance between LV pacing sites.
Further, quadrupole or multi-electrode LV leads have been found to afford more LV pacing vector options. Different pacing vector options may be chosen in order to avoid high capture thresholds and phrenic nerve stimulation and to select a preferred LV pacing site. Today, various device-based algorithms exist for automatically determining the LV pacing thresholds based on changes in evoked responses. However, existing automatic threshold determining techniques utilize an extended period of time, relative to conventional bipolar leads, when determining capture thresholds for a large number of LV pacing vectors (e.g. 10 or more vectors).
A need remains for improved methods and systems that automatically identify capture thresholds and reduce the time utilized for identifying available LV pacing vectors.